Non-Patent Literatures 1 and 2 disclose a technique referred to as OpenFlow in which control and data planes are separated from each other. In OpenFlow, a control apparatus referred to as an OpenFlow controller sets control information (flow entries) that defines packet forwarding rules and/or header conversion rules in target switches, and these switches process received packets by referring to the control information.
Non-Patent Literature 3 proposes a switch virtualization technique referred to as FlowVisor, as an extended technique of the above OpenFlow. In FlowVisor, a relay apparatus referred to as a FlowVisor is arranged between a plurality of OpenFlow controllers and a plurality of switches. The FlowVisor intercepts a control message issued from an OpenFlow controller and determines whether to set information in a corresponding switch in accordance with a resource allocation policy. In addition, the FlowVisor forwards a control message issued from a switch to a corresponding network controller in accordance with a resource allocation policy.
Non-Patent Literature 1:
    Nick McKeown, and seven others, “OpenFlow: Enabling Innovation in Campus Networks,” [online], [searched on Jan. 9, 2013], Internet <URL: http://www.openflow.org/documents/openflow-wp-latest.pdf>.Non-Patent Literature 2:    “OpenFlow Switch Specification” Version 1.3.1 (Wire Protocol 0x04), [online], [searched on Jan. 9, 2013], Internet <URL: https://www.opennetworking.org/images/stories/downloads/specification/openflow-spec-v1.3.1.pdf>.Non-Patent Literature 3:    “FlowVisor: A Network Virtualization Layer,” [online], [searched on Jan. 9, 2013], Internet <http://www.openflow.org/downloads/technicalreports/openflow-tr-2009-1-flowvisor.pdf>.